System and Method for Structural Restraint Against Seismic and Storm Damage

ABSTRACT

A system for structural restraint of wood framed structures against seismic and storm damage comprises a plurality of structural wood framing components; a plurality of structural wood sheathing components; a plurality of structural wood fasteners; one or more structural foundations; and a structural bonding agent applied to the interior and exterior over top of and in direct contact with structural fasteners to prevent failure of structural wood fasteners.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to wood framed construction systems. Inparticular, the present invention relates to a restraint system forreinforcement of wood framed buildings against seismic and storm damageby reinforcing the structural wood fastener locations.

BACKGROUND OF THE INVENTION

Much of the world's population is located along seismic fault lines orin the paths of powerful storms such as hurricanes, monsoons, floods andtornadoes. The buildings in such areas are at risk of structural damagefrom seismic and storm events. As these population centers grow, therisk of loss of life and damage to structures will only increase.

During powerful seismic and storm events, prior art wood framedconstruction techniques do not adequately hold the structural buildingcomponents together. Although such wood framed structures are among thesafest currently available, powerful seismic and storm events may resultin the failure of their structural integrity through the failure of thestructural wood fasteners. The primary reason for structural failure isthe inability of the structural fasteners to keep the structural woodsheathing firmly attached to the structural wood framing. As structuralfasteners primarily are designed to be static devices, they are likelyto fail when subjected to dynamic forces.

Many jurisdictions are seeking ways to mitigate the effects of thesepowerful seismic and storm events through the upgrading of buildingcodes. To date, nothing has been available to solve the problemsassociated with these events. Governments, as well as construction,insurance and forest industries and the general population, all have agreat deal to benefit from a solution to these damaging effects.

As powerful seismic and storm events act on a structure, the threedimensional dynamic forces compromise the structural wood fasteners,causing them to work their way loose or out of the members in which theyare embedded or, if they remain in place, they may tear their waythrough the structural wood sheathing or simply break off. The result isthe weakening or complete loss of structural integrity of the woodframed building as the structural forces no longer are able to betransferred safely down to the structural foundations.

During powerful seismic and storm events failure points occur primarilyalong structural wood fastener strips of structural wood sheathing.These failure points may be at corners, at intersections, around door,window and other openings, at vertical joints, and along horizontaljoints at floor and ceiling edges.

Presently there are no systems or structural wood fasteners which canprevent these failures. Existing prior art solutions use a form ofbuilding restraint consisting of a complex engineered system of steelrods, anchors, plates and straps requiring extensive notching, drillingand additional structural reinforcement. Installation of such a systemmay interfere significantly with construction schedules in thatelectrical, plumbing and other sub-trades will have their work suspendedwhile the required building modifications are carried out. This form ofrestraint system fails to provide a solution to the problem ofstructural wood fasteners breaking off or pulling loose, out or throughthe structural wood sheathing, putting at risk the structural integrityof the wood framed structure.

The restraint system of the present invention provides a solution whichmaintains the integrity of the structural wood fasteners. This resultsin the structural wood sheathing remaining firmly attached to thestructural wood framing and the structural foundations. The integrity ofthe entire wood framed structure is maintained and the structural loadsare able to be transferred safely down to the structural foundation.

SUMMARY OF THE INVENTION

There is provided a system for structural restraint of wood framedstructures against seismic and storm damage, the system comprising aplurality of structural wood framing components; a plurality ofstructural wood sheathing components; a plurality of structural woodfasteners; one or more structural foundations; and a structural bondingagent.

The structural bonding agent may be a thermoset polyurea elastomerhaving a tensile strength of at least 15 MPa (2000 psi) and may have anelastomeric flexural strength of at least 300%. The structural bondingagent may remain flexible to temperatures as low as −40° C. (−40° F.).

There is further provided the use of a structural bonding agent toreinforce wood framed building structures against seismic and stormdamage by preventing egress of structural wood fasteners from structuralwood framed building components. The structural bonding agent used maybe a thermoset polyurea elastomer.

The invention further comprises a method of reinforcing a wood framedstructure against seismic or storm damage comprising the steps of woodframing a desired structure; applying a structural flexible bondingagent to completely cover over structural wood fasteners and be indirect contact with the external end of each fastener at selectedlocations of the wood framed structure to achieve a desired thickness.

The bonding agent may be applied by spraying. The flexible bonding agentmay be applied to an area of between 100 mm (4″) and 255 mm (10″) widecentered over the structural wood fastener components.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of the preferred embodiments is provided by wayof example only and with reference to the following drawings, in which:

FIGS. 1A and 1B are cross-sectional views of two exterior walls of abuilding extending between structural foundation wall and roof truss,one (1B) of which depicts door and window openings, according to oneembodiment of the present invention;

FIG. 2 is a cross-sectional view of the assembly of a wall stud, floorjoist and structural foundation wall, according to one embodiment of thepresent invention;

FIG. 3 is a cross-sectional view of an assembly of a wall stud, floorjoist and structural foundation wall including a door opening, accordingto one embodiment of the present invention;

FIG. 4 is a cross-sectional view of an assembly of a lower level wallstud, floor joist, and upper level wall stud above a door opening,according to one embodiment of the present invention;

FIG. 5 is a cross-sectional view of an assembly of a lower level wallstud, floor joist, and upper level wall stud, according to oneembodiment of the present invention;

FIG. 6 is a cross-sectional view of a wall stud adjacent a windowopening, according to one embodiment of the present invention;

FIG. 7 is a cross-sectional view of a wall stud and roof truss,according to one embodiment of the present invention;

FIG. 8 is a cross-sectional view of a wall stud and roof truss above awindow opening, according to one embodiment of the present invention;

FIG. 9 is a front plan view of sections A, B and C of a structural wall,according to one embodiment of the present invention;

FIGS. 10A, 10B, and 10C are cross sectional views of corresponding wallsections A, B, and C of FIG. 9, according to one embodiment of thepresent invention;

FIG. 11A depicts a top view cross section of a wall configurationconsisting of a 90 degree framed exterior corner;

FIG. 11B depicts a top view cross section of a wall configurationconsisting of a 90 degree framed exterior corner, two 45 degree framedexterior corners and a 90 degree framed interior corner; and

FIG. 11C depicts a top view cross section of a wall configurationconsisting of two typical 45 degree framed interior corners; accordingto one embodiment of the present invention.

In the drawings, one embodiment of the invention is illustrated by wayof example. It is to be expressly understood that the description anddrawings are only for the purpose of illustration and as an aid tounderstanding, and are not intended as a definition of the limits of theinvention.

For the purposes of clarity the structural wood fasteners have not beenshown as specific locations may be different from what would be shown.It is understood through description that the structural bonding agentmay be applied to an area of between 100 mm (4″) and 255 mm (10″) widecentered over top of the structural wood fastener components.

DETAILED DESCRIPTION OF THE INVENTION

There is provided a structural restraint system to maintain wood framedbuilding structural integrity during powerful seismic and storm events.The restraint system of the present invention reduces or eliminatesstructural wood fastener failure, whether through breakage, loosening,detachment, or rupture through the structural wood framed componentsthey are meant to secure. This result is achieved by providing a layerof a structural bonding agent over top of the structural fasteners so asto sandwich the external ends of the fasteners between the structuralframe and the structural bonding agent. The presence of the structuralbonding agent over top of the ends of the fasteners prevents egress ofthe fasteners from the structural framing components.

The restraint system of the present invention comprises five wood framedstructural building components. These five structural buildingcomponents are wood framing, wood sheathing, structural wood fasteners,a structural foundation, and a flexible bonding agent.

The structural wood framing may be manufactured of wood or compositewood materials and combinations thereof structural Framing componentsmay include studs, posts, plates, joists, rafters, beams, lintels, builtup assemblies and trusses.

The structural wood sheathing may be manufactured of wood, plank,plywood, oriented strand board (OSB), wafer board, composite boards andother structural membranes for walls, roofs and floors;

Each structural wood fastener (25) may be a hardware device thatmechanically joins two or more structural components together, forexample, nails, staples, screws. In the drawings, nails are depicted.

The foundation may be constructed of concrete, masonry, treated wood, orother approved material

A suitable flexible bonding agent may be a spray-applied structuralflexible elastomer, for example polyurea or equivalent. The flexiblebonding agent is applied to corresponding interior and exterior portionsof the structure as noted on the diagrams and as previously described.The flexible bonding agent ideally should be rapid thermosetting, havefast reactivity, be relatively insensitive to moisture, and be fullycurable in high humidity, cold or moist substrate conditions. Theflexible bonding agent should have a tensile strength of 2200 to 2500psi for thermoset elastomer. The flexible bonding agent should have anelongation range of 300% to 600% elongation flexural strength forsprayed elastomer, and should adhere tenaciously to multiple substratesincluding wood, composites and concrete. It should remain flexible attemperatures as low as −40° C. (−40° F.), and should permit applicationof multiple coats over one another. According to one embodiment, thesprayed elastomer may have Shore D hardness rating of between 54.5 and55.5. Other hardness ratings are also possible within the scope of theinvention.

Existing prior art wood framed building restraint systems are designedto lessen the effects of powerful seismic and storm events only to theextent necessary to maintain structural integrity long enough to permitevacuation or rescue to save lives. The structure itself may sufferextensive damage and require extensive repairs to reattach thestructural wood sheathing, or the building may be condemned todemolition. In contrast, the restraint system of the present inventionnot only maintains structural integrity to the extent necessary for thestructure to survive one powerful seismic or storm event, but to survivemultiple such events. The restraint system of the present inventionachieves this improved outcome by holding the structural wood fastenersin place during the seismic or storm event so they can effectivelyperform their function of maintaining the structural integrity of thewood framed building. The fasteners are held in place by the applicationof a flexible bonding agent completely over the structural fasteners andin direct contact with the external end of each fastener, after it hasbeen used to fasten together structural components.

The restraint system of the present invention is easy to apply toexisting or new wood framed structures, greatly reduces the costs ofseismic upgrades to wood framed buildings, does not interfere withconstruction schedules, and is highly effective in preventing structuralwood fasteners from working their way loose, out or through thestructural wood sheathing, or breaking off entirely.

The system is able to compensate for natural settling and shrinkage ofwood framed structures, and is applicable to all site and factoryassembled, platform or balloon framed, wood construction for single andmulti-family residential, commercial, industrial and institutionalstructures, whether single or multi story structures.

The restraint system of the present invention is compatible withbuilding codes around the world. The degree of protection may beadjusted to meet the design parameters for a particular structure.Increased protection may be achieved by increasing the width of sprayapplication as previously described, or by applying multiple coats toincrease the thickness of the bonding agent.

According to the present invention, the sprayed polyurea elastomer isapplied to the interior as well as the exterior of a wood framedbuilding structure.

In operation, at wood framing completion or at the completion of aphased portion of the wood framed construction, the structural flexiblebonding agent is applied in a generally linear spray pattern at aplurality of locations specified in the figures. These locations includealong the length of framing components and over top of fasteners whereapplied through external sheathing. The flexible bonding agent isapplied generally in a linear spray pattern approximately 100 mm (4″) to255 mm (10″) wide and centered over the structural wood fastenercomponents that are being covered and restrained. The structuralflexible bonding agent should be applied approximately 5 mm-7 mm (3/16″-¼″) thick. Special care should be taken to ensure the structuralwood fastener strips are covered.

Wherever structural wood fasteners are used to connect together two ormore structural wood components, the flexible bonding agent may beapplied over the fasteners to prevent the fasteners from losing theirfunction during a seismic or storm event. The structural flexiblebonding agent will ensure the structural fasteners are prevented fromworking loose, out or through the structural wood sheathing, or breakingoff, thus maintaining the connection of the fastener to the structuralwood framing. The restraint system of the present invention acts tocompletely integrate the structural wood framed components and bindsthem together as a single unit.

Referring now to FIGS. 2 and 3, these drawings depict a wall stud (1)vertically disposed above a subfloor (3), which is over a floor joist(4). Adjacent the exterior wall surface, a floor rim joist (5) abuts thefloor joist. Wall sheathing (6) is applied to the exterior of the wallstud. An anchor bolt assembly (8) passes through a sill plate (9) andsill plate gasket (10) or equivalent into a structural foundation wall(11). In FIG. 2, a top or bottom wall plate (2) is shown below the wallstud. As previously noted the structural wood fasteners have not beenshown in the diagrams for sake of clarity as specific locations of thestructural wood fasteners may vary. In general the location of theflexible bonding agent is centered over the structural wood fasteners.This is applicable to all the diagrams.

According to the present invention, a structural flexible bonding agent(7) is spray applied adjacent selected wood framed connection pointsbetween structural wood framed components. As shown in FIG. 2, theflexible bonding agent is applied at the interior lower end of thestructural wall sheathing along the area at which it is adjacent thestructural wall plate, as well as along the exterior of the area atwhich the structural wall sheathing is in proximity to the structuralsubfloor and the structural floor rim joist, and along the area at whichthe structural floor rim joist, structural sill plate, sill plate gasketand structural foundation wall are adjacent. FIG. 3 depicts applicationof the flexible bonding agent along the exterior of the area at whichthe structural wall sheathing is in proximity to the structuralsubfloor, and the structural floor joist, and along the area at whichthe structural floor rim joist, structural sill plate, sill plate gasketand structural foundation wall are adjacent.

Referring now to FIG. 4, the flexible bonding agent of the restraintsystem is depicted applied along the connection area between thestructural wall sheathing and the structural wall plate; exterior to thestructural wall sheathing, structural subfloor and structural floor rimjoist; exterior to the structural floor rim joist, structural wall plateand structural wall sheathing, and along the connection between thestructural wall sheathing, a structural lintel sill opening (14) and astructural jack stud opening (15). FIG. 4 depicts a structural lintelopening (12) and a lintel space opening (13) above the lintel sillopening.

Referring now to FIG. 5, the flexible bonding agent of the restraintsystem is depicted applied along the connection area between thestructural wall sheathing and the structural wall plate for an upperlevel; exterior to the structural wall sheathing, structural subfloorand structural floor rim joist; exterior to the structural floor rimjoist, structural wall plate and structural wall sheathing, and alongthe connection between the structural wall sheathing and a structuralwall plate for a lower level.

Referring now to FIG. 6, a jack stud opening is shown above a sillopening (17) disposed above a trimmer stud opening (18). The flexiblebonding agent is applied into the jack stud opening, along theconnection area between the structural wall sheathing and the top of thesill opening, and along the connection area between the interior of thestructural wall sheathing and the bottom of the sill opening.

Referring now to FIG. 7, the top of a structural wall stud is shownwhere it is adjacent a structural roof truss (20). Structural roofsheathing (21) is disposed above the structural roof truss. Flexiblebonding agent may be applied between the interior of the structural wallsheathing and bottom of a structural wall plate, along the exterior ofthe structural wall sheathing where it is adjacent the structural rooftruss, and between the structural roof truss and structural roofsheathing.

Referring now to FIG. 8, flexible bonding agent may be applied betweenthe structural roof truss and structural roof sheathing, along theexterior of the structural wall sheathing where it meets the structuralroof truss, along the exterior of the structural wall sheathing where itmeets the lintel sill opening, and into a jack stud opening.

Referring now to FIG. 9, an interior view of a framed wall with a windowand a door is depicted, showing the interior component of the sprayedelastomer as viewed from the interior. The section marked “A” depicts aportion of wall which contains a framed window opening. The sectionmarked “B” depicts a portion of wall which contains an exterior verticaljoint of the structural sheathing, and the section marked “C” depicts asection of wall which contains a framed door opening. FIG. 10A, 10B, and10C show top view cross sections, below the top plates of the wall, ofsection “A”, section “B” and section “C”, respectively, of FIG. 9,including openings for jack studs (15), king studs (16), and trimmerstuds (18).

FIGS. 11A, 11B, and 11C show the application of the interior andexterior bonding agent components at typical vertical structuralsheathing joints and at a framed exterior corner.

It will be appreciated by those skilled in the art that other variationsof the preferred embodiment may also be practiced without departing fromthe scope of the invention.

1. A system for structural restraint of wood framed structures againstseismic and storm damage, the system comprising a structure built from aplurality of structural wood framing components, a plurality ofstructural wood sheathing components, and one or more structuralfoundations; a plurality of structural wood fasteners, each structuralwood fastener connecting together two or more of the structural woodframing components, structural wood sheathing components, or structuralfoundations; and a structural bonding agent, wherein the structuralbonding agent is applied to the structural wood framing components,structural wood sheathing components, and structural foundationscompletely covering over the structural wood fasteners and in directcontact with the external end of each structural wood fastener toprevent egress of the structural wood fasteners.
 2. The system of claim1, wherein the structural bonding agent is a polyurea thermosetelastomer having a tensile strength of at least 2200 psi.
 3. The systemof claim 1 wherein the structural bonding agent has an elastomericflexural strength of at least 300%.
 4. The system of claim 1, whereinthe structural bonding agent remains flexible to temperatures as low as−40° C. (−40° F.).
 5. Use of a structural bonding agent to reinforcewood-framed building structures against seismic and storm damage byapplying the structural bonding agent in direct contact with, and tocompletely cover over structural wood fasteners to prevent egress of thestructural wood fasteners from structural wood framed buildingcomponents.
 6. The use of the structural bonding agent as in claim 5,wherein the structural bonding agent is a polyurea thermoset elastomer.7. A method of reinforcing a wood framed structure against seismic orstorm damage comprising the steps of: wood framing a desired structure;and applying a structural flexible bonding agent to completely coverover structural wood fasteners at selected locations of the wood framedstructure to achieve a desired thickness, wherein the structuralflexible bonding agent is in direct contact with and completely coversover the external end of each structural wood fastener.
 8. The method ofclaim 7, wherein the flexible structural bonding agent is applied byspraying.
 9. The method of claim 7, wherein the flexible bonding agentis applied to an area of between 100 mm (4″) and 255 mm (10″) widecentered over top of the structural wood fasteners, and in directcontact with the external end of each structural wood fastener.
 10. Themethod of claim 7, wherein the flexible structural bonding agent isapplied to selected locations on the interior of the framed structure,and corresponding selected locations on the exterior of the framedstructure.
 11. The method of claim 10, wherein the flexible structuralbonding agent applied to selected locations on the interior of theframed structure is a polyurea thermoset elastomer, and the flexiblebonding agent applied to corresponding selected locations on theexterior of the framed structure is a spray foam insulation polyureathermoset elastomer.